东北森林关键生态系统服务权衡对气候变化与林火干扰的响应机制

Ecosystem service tradeoffs and their responses to natural disturbances are hotspots in current research of ecology and physical geography. However, there are still many uncertainties in the study of ecosystem services and their influence factors from the perspective of interrelationships between multiple service types. This project selects the forest ecosystem in Northeast China that is strategically important to ensure national ecological security, and focuses on two key types of ecosystem services: carbon sequestration and water conservation. By the comprehensive applications of field investigation, statistical analysis and model simulation, the project is designed as follows. Firstly, the relationship between forest runoff and carbon sequestration will be studied on the sample plot scale, and the response mechanism to climate change will be revealed through sensitivity analysis. And then, the tradeoffs relationship between water conservation and forest carbon sequestration services will be quantitatively characterized on the regional scale, and the change characteristics of ecosystem services tradeoffs of different periods from past to future will be discussed. Finally, the scenario analysis method is performed to explore the impact mechanism and dominant factors of climate change and fire disturbance on the tradeoffs of forest ecosystem services in Northeast China. Furthermore, spatial heterogeneity and quantitative attribution of the response to climate change and fire disturbance will be identified by geographically weighted regression and geographic detector. Through the above study, it is expected to provide scientific support for optimizing the sustainable management of forest ecosystem in Northeast China and formulating relevant policies.

生态系统服务权衡及其对自然干扰的响应是当前生态学与自然地理学研究的热点，然而从多种服务类型相互关系的角度开展生态系统服务及其影响因素的研究仍存在诸多不确定性。本项目选取对保障国家生态安全具有战略意义的东北森林生态系统，围绕森林固碳与水源涵养两项关键的生态系统服务类型，综合野外调查、统计分析以及模型模拟等技术手段，首先在样地尺度上分析森林固碳与产流的相互关系，并通过敏感性分析揭示其对气候变化的响应机理；进而在区域尺度上对水源涵养和森林固碳服务权衡关系进行定量化表征，并探究过去到未来不同时期生态系统服务权衡的变化特征；最后通过情景分析法探讨气候变化及其引起的火干扰改变对东北森林生态系统服务权衡的影响机制和主控因子，并辅以地理加权回归和地理探测器方法识别权衡关系对气候变化与林火干扰响应的空间异质性及定量归因。通过上述研究内容，以期为优化东北森林生态系统的可持续管理以及制定相关的政策提供科学支撑。

本项目关注东北森林固碳与水源涵养两项关键生态系统服务，综合野外调查、统计分析与模型模拟等手段，首先在样地尺度模拟固碳与产流，并对模型验证优化；进而在区域尺度对水源涵养与固碳的权衡/协同定量表征，探究过去到未来的变化特征；最后揭示气候变化与林火干扰对权衡/协同关系影响的空间分异及定量归因。研究表明，东北森林的固碳增汇潜力较大，未来水源涵养与固碳关系减弱，气候变化是影响二者权衡/协同的主导因素，而未来林火干扰的作用增强，二者的叠加将大幅提高其对东北森林的影响。具体表现为：（1）大兴安岭地区：地表径流持续下降，壤中流上升速率最快，水源涵养对气候变化主要为正敏感性。南部地区固碳速率下降，且下降范围不断北移，而未来对气候变化的敏感性转为正值。过去时期南部地区固碳与地表径流的协同较强，而与壤中流在整个区域均为权衡；未来中南部地区的固碳与壤中流转为协同关系，主要由增温和降水减少所引起。未来林火发生密度的增加将会减弱固碳与产水的权衡。（2）小兴安岭地区：未来水源涵养对增温转为正敏感性，而壤中流对降水变化则转为负敏感性。北部地区固碳速率下降，对增温转为正敏感性。过去时期固碳与地表径流主要是协同关系，而与壤中流则以权衡为主；未来固碳与壤中流转为协同关系。未来增温与降水增加将导致固碳与产水协同的减弱，而林火强度的改变也将减弱协同关系。（3）长白山地区：水源涵养能力最强，但地表径流下降速率最快，对增温以负敏感性为主，而壤中流对增温多为正敏感性。东部地区固碳增长速率较快，对降水变化主要以负敏感性为主，未来东部地区对增温则转为负敏感性。过去时期固碳与产水主要表现为协同关系，但未来与壤中流则转为权衡。未来增温与降水增加将导致固碳与地表径流关系的减弱，而燃烧率的增加则是导致固碳与壤中流权衡减弱的主要因素。项目成果有利于推动东北森林资源的高效利用，对于优化森林管理，发挥碳汇功能，减缓全球变暖均具有重要意义。